PID.h

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// /**
//  * @author Aaron Berk
//  *
//  * @section LICENSE
//  *
//  * Copyright (c) 2010 ARM Limited
//  *
//  * Permission is hereby granted, free of charge, to any person obtaining a copy
//  * of this software and associated documentation files (the "Software"), to deal
//  * in the Software without restriction, including without limitation the rights
//  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  * copies of the Software, and to permit persons to whom the Software is
//  * furnished to do so, subject to the following conditions:
//  *
//  * The above copyright notice and this permission notice shall be included in
//  * all copies or substantial portions of the Software.
//  *
//  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  * THE SOFTWARE.
//  *
//  * @section DESCRIPTION
//  *
//  * A PID controller is a widely used feedback controller commonly found in
//  * industry.
//  *
//  * This library is a port of Brett Beauregard's Arduino PID library:
//  *
//  *  http://www.arduino.cc/playground/Code/PIDLibrary
//  *
//  * The wikipedia article on PID controllers is a good place to start on
//  * understanding how they work:
//  *
//  *  http://en.wikipedia.org/wiki/PID_controller
//  *
//  * For a clear and elegant explanation of how to implement and tune a
//  * controller, the controlguru website by Douglas J. Cooper (who also happened
//  * to be Brett's controls professor) is an excellent reference:
//  *
//  *  http://www.controlguru.com/
//  */
 
#ifndef _PID_H_
#define _PID_H_
 
#include "debug1.h"
#include "helper.h"
#include "mbed.h"
 
class PID {
  public:
    PID(float Kc, float tauI, float tauD, float interval);
 
    void setInputLimits(float inMin, float inMax);
 
    void setOutputLimits(float outMin, float outMax);
 
    void setTunings(float Kc, float tauI, float tauD);
 
    void reset();
 
    void setSetPoint(float sp);
 
    float getSetPoint();
 
    void setProcessValue(float pv);
 
    void setBias(float bias);
 
    float compute(void);
 
  protected:
    bool _usingFeedForward;
 
    // Actual tuning parameters used in PID calculation.
    float _Kc;
    float _tauR;
    float _tauD;
 
    // Raw tuning parameters.
    float _pParam;
    float _iParam;
    float _dParam;
 
    // The point we want to reach.
    float _setPoint;
    // The thing we measure.
    float _processVariable;
    float _prevProcessVariable;
    float _prevError;
    // The output that affects the process variable.
    float _controllerOutput;
    float _prevControllerOutput;
 
    // We work in % for calculations so these will scale from
    // real world values to 0-100% and back again.
    float _inMin;
    float _inMax;
    float _inSpan;
    float _outMin;
    float _outMax;
    float _outSpan;
 
    // The accumulated error, i.e. integral.
    float _accError;
    // The controller output bias.
    float _bias;
 
    // The exponential filter alpha
    float _a;
 
    // The interval between samples.
    float _tSample;
 
};
 
#endif  // _PID_H_